45 West Nile cases reported in O.C. this year

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HUNTINGTON BEACH Forty-five people in Orange County have been infected with the mosquito-borne West Nile virus so far this year.

This year has seen the highest number of West Nile cases in Orange County since 2008, when 71 people were infected. In 2009, four cases were reported countywide, followed by one case in 2010, and 10 cases in 2011, according to county officials.

“Right now it looks like the virus is trending at about a four-year cycle – in 2004, in 2008 and 2012 we've seen spikes in human cases in Orange County,” said Jared Dever, director of communications for Orange County Vector Control. “With 45 human infections this year, that's quite high. It's certainly not our highest year … but it's quite a bit higher.”

The Orange County Health Care Agency works with Vector Control to educate cities and control and monitor mosquito populations.

“You have to realize that not only do we see cases of illness, but we'll see a fair number of people who get neuroinvasive disease – that means either meningitis or encephalitis. That's brain infection that can make people seriously ill,” said Matt Zahn, the health agency's medical director of epidemiology. “It's certainly a concern, particularly because it's preventable. If people take common-sense measures to avoid being bitten by mosquitoes, then they can mitigate their risk. … That's the goal that we have for sure.”

MOSQUITO CARRIERS

West Nile virus is a disease carried by mosquitoes that contract the virus from feeding on the blood of infected birds, passing the virus along to humans when the insects bite. There is no effective treatment or vaccine.

“The majority of people who are infected will have no symptoms. Eighty percent of people won't have any symptoms, 20 percent will, and most of those persons will have fever and other nonspecific symptoms like headaches and muscle aches,” Zahn said. “That illness is unpleasant for people but will get better and resolve on its own. Less than 1 percent of people will get encephalitis, and encephalitis is the illness to really be concerned about with West Nile.”

Dever said the amount of cases correlates with the evening temperatures in the winter. Warmer weather during winter nights allows mosquitoes to continue breeding through the winter, increasing the likelihood of West Nile virus.

“We track and monitor thousands and thousands of mosquito breeding sources – any pool of water down to the size of a thimble or a bad backyard swimming pool, or estuaries and tidal lagoons that we have here in Orange County. We track and monitor all these sources throughout the year,” Dever said. “We monitor them for breeding and we treat them when they do have breeding that's occurring in those sources.”

Orange County Vector Control District staff monitors the various sources through personally visiting the sites and using aerial surveillance aircrafts to shoot high-resolution photos of areas. The agency also utilizes an underground team to monitor manholes and storm drains, where up to 10,000 mosquitoes can be found hiding during the day, he said.

“It's a 365-day-a-year job to suppress the population of mosquitoes. The more mosquitoes that we can prevent from hatching and becoming adults, the less of a risk there is for contracting West Nile virus,” said Dever. “The ultimate goal is to bring down the population to a number, a threshold, where there's just not quite enough of them out there where humans are going to encounter them very often.”

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